1. Field of the Invention
The invention relates to a magnetic transducer and a thin film magnetic head using the same. More particularly, the invention relates to a magnetic transducer which can obtain a higher rate of resistance change and a larger magnitude of resistance change and also has higher stability of properties, and a thin film magnetic head using the magnetic transducer.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk or the like. A composite thin film magnetic head, which has a stacked structure comprising a reproducing head having a magnetoresistive element (hereinafter referred to as an MR element) that is a type of magnetic transducer and a recording head having an inductive magnetic transducer, is widely used as the thin film magnetic head.
MR elements include an AMR element using a magnetic film (an AMR film) exhibiting an anisotropic magnetoresistive effect (an AMR effect), a GMR element using a magnetic film (a GMR film) exhibiting a giant magnetoresistive effect (a GMR effect), and so on.
The reproducing head using the AMR element is called an AMR head, and the reproducing head using the GMR element is called a GMR head. The AMR head is used as the reproducing head whose surface recording density exceeds 1 Gbit/inch2, and the GMR head is used as the reproducing head whose surface recording density exceeds 3 Gbit/inch2.
As the GMR film, a xe2x80x9cmultilayered (antiferromagnetic)xe2x80x9d film, an xe2x80x9cinductive ferrimagneticxe2x80x9d film, a xe2x80x9cgranularxe2x80x9d film, a xe2x80x9cspin valvexe2x80x9d film and the like are proposed. Of these types of films, the spin valve type GMR film is considered to have a relatively simple structure, to exhibit a great change in resistance even under a low magnetic field and to be suitable for mass production.
FIG. 20 shows the structure of a general spin valve type GMR film (hereinafter referred to as a spin valve film). A surface indicated by reference symbol S in FIG. 20 corresponds to a surface facing a magnetic recording medium. The spin valve film has a stacked structure comprising an underlayer 801, a soft magnetic layer 802, a nonmagnetic layer 803, a ferromagnetic layer 804, an antiferromagnetic layer 805 and a cap layer 806, which are stacked in this order on the underlayer 801. In the spin valve film, the orientation of magnetization Mp of the ferromagnetic layer 804 is fixed by exchange coupling between the ferromagnetic layer 804 and the antiferromagnetic layer 805. The orientation of magnetization Mf of the soft magnetic layer 802 freely changes according to an external magnetic field. Resistance of the spin valve film changes according to a relative angle between the orientation of the magnetization Mp of the ferromagnetic layer 804 and the orientation of the magnetization Mf of the soft magnetic layer 802.
In recent years, magnetic recording at ultra-high density in excess of 20 Gbit/inch2 has required a further increase of the rate of change in electrical resistance of the spin valve film (hereinafter referred to as the rate of resistance change). Moreover, the increase of output of the thin film magnetic head has required the increase of the amount of change in resistance of the spin valve film (hereinafter referred to as the magnitude of resistance change). Reducing a thickness of the soft magnetic layer enables increasing the rate of resistance change and the magnitude of resistance change. However, there is a problem that output variations occur and properties such as output symmetry are not stable.
Therefore, the rate of resistance change is increased by inserting an oxide film called NOL into a ferromagnetic layer of a spin valve film, which is proposed in the cited reference xe2x80x9cCoFe specular spin valves with a nano oxide layerxe2x80x9d, 1999 Digests of INTERMAG 99, published on May 18, 1999 (hereinafter referred to as the cited reference 1). Moreover, a back-layer made of Cu (copper) is provided on the side of a soft magnetic layer opposite to a nonmagnetic layer, which is proposed in, for example, the cited reference xe2x80x9cRead-write performance of the spin-filter-spin-valve headsxe2x80x9d, p. 402, the Proceedings of the Annual Meeting of THE MAGNETICS SOCIETY OF JAPAN (hereinafter referred to as the cited reference 2). Similarly, a back-layer made of nonmagnetic metal is provided on the side of a soft magnetic layer opposite to a nonmagnetic layer, which is proposed in U.S. Pat. No. 5,422,571 (hereinafter referred to as the cited reference 3).
However, the above-mentioned cited reference 1 gives no descriptions about specific conditions such as a material and thickness of the oxide film called NOL and a position into which the oxide film is to be inserted, and any properties other than the rate of resistance change. It is therefore necessary to study these conditions and properties. Moreover, methods described in the above-mentioned cited references 2 and 3 have a problem that the magnitude of resistance change cannot be sufficiently increased.
The invention is designed to overcome the foregoing problems. It is an object of the invention to provide a magnetic transducer which can obtain a higher rate of resistance change and a larger magnitude of resistance change and also has higher stability of properties, and a thin film magnetic head using the magnetic transducer.
A magnetic transducer of the invention comprises: a first nonmagnetic layer having a pair of surfaces opposing each other; a soft magnetic layer formed on one surface of the first nonmagnetic layer; a ferromagnetic layer formed on the other surface of the first nonmagnetic layer; an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the first nonmagnetic layer; a second nonmagnetic layer formed on the soft magnetic layer on the side opposite to the first nonmagnetic layer; and a high-resistance layer located on the second nonmagnetic layer on the side opposite to the soft magnetic layer and made of a material having resistivity of 200 xcexcxcexa9xc2x7cm or more.
In the magnetic transducer of the invention, the high-resistance layer is located on the second nonmagnetic layer on the side opposite to the soft magnetic layer and is made of a material having resistivity of 200 xcexa9xc2x7cm or more. Therefore, the rate of resistance change and the magnitude of resistance change are increased, and stability of properties is also improved.
Preferably, the high-resistance layer contains at least one element in a group consisting of Al (aluminum), Cr (chromium), Ti (titanium), Ru (ruthenium), Mn (manganese), Rh (rhodium), Ag (silver), Pd (palladium), Ni (nickel), Cu (copper), Co (cobalt), Fe (iron), Re (rhenium) and Ta (tantalum), and at least one element in a group consisting of O (oxygen) and N (nitrogen). More preferably, the high-resistance layer contains at least one element in a group consisting of Al, Cr, Ti, Ru, Mn and Rh.
Preferably, a thickness of the high-resistance layer is from 0.5 nm to 30 nm inclusive. Preferably, the second nonmagnetic layer contains at least one element in a group consisting of Au (gold), Ag (silver), Cu, Ru, Rh, Re, Pt (platinum) and W (tungsten). Preferably, a thickness of the second nonmagnetic layer is from 0.5 nm to 2 nm inclusive.
Preferably, the ferromagnetic layer can have two magnetizations which are opposite each other in direction. Preferably, the ferromagnetic layer includes a ferromagnetic inner layer, an ferromagnetic outer layer, and a coupling layer sandwiched between the ferromagnetic inner layer and the ferromagnetic outer layer. More preferably, a magnetic interlayer having higher electrical resistance than that of at least a part of the ferromagnetic layer is provided in the ferromagnetic layer. Preferably, a thickness of the soft magnetic layer is from 1 nm to 6 nm inclusive.
A thin film magnetic head of the invention has the above-described magnetic transducer.
Another thin film magnetic head of the invention has a magnetic transducer between a pair of magnetic layers with a pair of gap layers in between, the magnetic transducer comprising: a first nonmagnetic layer having a pair of surfaces opposing each other; a soft magnetic layer formed on one surface of the first nonmagnetic layer; a ferromagnetic layer formed on the other surface of the first nonmagnetic layer; an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the first nonmagnetic layer; a second nonmagnetic layer formed on the soft magnetic layer on the side opposite to the first nonmagnetic layer, wherein one of the pair of gap layers is located on the second nonmagnetic layer and is made of a material having resistivity of 200 xcexcxcexa9xc2x7cm or more.
Other and further objects, features and advantages of the invention will appear more fully from the following description.